This invention relates to ultrasonic proximity sensors and, more particularly, to an improved ultrasonic proximity sensor utilizing polymer piezoelectric film in the transducer assembly.
Proximity sensors have many applications. For example, a proximity sensor mounted to a vehicle can provide a warning to the vehicle operator of the presence of an obstruction in the path of the vehicle. Thus, a proximity sensor mounted to the rear of a truck which is backing toward a loading dock can be utilized to alert the truck driver of the remaining distance to the loading dock. It is therefore an object of the present invention to provide a proximity sensor which may be utilized for such an application.
A proximity sensor utilizing radiated and reflected ultrasonic acoustic waves is a desirable form for use in such an application. The desired beam pattern for obstruction detection applications is a straight, wide and thin beam. It is therefore another object of the present invention to provide a transducer assembly for generating an ultrasonic acoustic wave having such desired beam pattern.
A proximity sensor mounted on the rear of a vehicle may be subject to damage by flying sand or stone particles from the road surface and physical impact, such as from brushes during washing of the vehicle for example. The proximity sensor will also be exposed to rain and cleaning water which may penetrate between the polymer piezoelectric film and a mounting assembly of the proximity sensor. It is therefore a further object of the invention to provide a durable ultrasonic proximity sensor utilizing a polymer piezoelectric film in a transducer assembly which is particularly suited for outdoor applications and capable of withstanding exposure to sand and stone particles, water, physical impact and similar conditions.